Based on a low-temperature route, monodispersed CoFe2O4 microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction/photoelectron spectroscopy, scanning/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe2O4 MSs with narrow size distribution can be tuned from over 200 to ~330 nm. Magnetic measurements reveal these MSs exhibit superparamagnetic behavior at room temperature with high saturation magnetization. Furthermore, the mechanism of formation of the monodispersed CoFe2O4 MSs was discussed on the basis of time-dependent experiments, in which hydrophilic PVP plays a crucial role.
The optical properties of composites, formed by filling the high density polyethylene (HDPE) with carbon black (CB), multi-walled carbon nanotubes (MWNTs) and fullerene (C60), respectively, in the frequence region from 0.3 to 2.0 terahertz (THz) were characterized with THz time-domain spectroscopy (THz-TDS). It is found that the optical parameters and the details of their variation with frequence and filler concentration are significantly different for different kinds of carbon materials. The MWNTs filled composites have the biggest absorption coefficient value, refractive index and real conductivity. The C60/HDPE composite shows very little changes in absorption and refractive index compared to that of the HDPE even at a filler-content of 12.3% in volume fraction. These phenomena are related to the special properties of the fillers as well as their particulate structures, such as aspect ratio, particle size, and aggregate structure, etc. The results are analyzed by using Cole-Cole theory of dipole relaxation under the assumption that carbon particles dispersed in the matrix behave like dipoles.
Bi2S3 flowerlike patterns were synthesized via a facile hydrothermal approach without using any surfactant and acid. The morphology, structure, phase composition, of the as-prepared Bi2S3 products were characterized using scanning electron microscopy, X-ray diffraction, high-resolution transmission and electron microscopy, respectively. The experimental results showed that the product possesses good distribution of morphology, well crystallized nanostructure.
The rheological and electrical properties of composites formed by filling high density polyethylene (HDPE) with carbon black (CB) were characterized. Nonuniversal electrical behavior was observed with critical exponent t of 2.9 for the composites. The phenomenon was interpreted in terms with tunneling-percolation model. The effects of shearing frequency and particle concentration on the rheological behavior of the composites were investigated. A second plateau of storage modulus and strong shear thinning behavior were observed at low frequencies induced by aggregation of fillers. And the rheological percolation threshold is found to coincide well with the electrical one.
To solve the communication problems in Command Information System, we introduced the Unified Communication technology which is developing rapidly in recent years, and analysised the feasibility of using this technology. We put forward a Unified Communication platform application model and made a preliminary study of its hierarchy and implementation.
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